FS

• Filesystem Hierarchy Standard

FileSystem

逻辑/内存

fs	mount point	notes
proc	/proc
sysfs	/sys
devfs	/dev	linux 4.16+ 废弃
devtmpfs	/dev	udev
cgroup	/sys/fs/cgroup
cgroup2	/sys/fs/cgroup/unified
cpuset	/sys/fs/cgroup/cpuset
debugfs	/sys/kernel/debug
bdev
tracefs
securityfs	/sys/kernel/security/	LSM - Linux Security Modules
sockfs		TCP/UDP sockets
bpf
hugetlbfs
devpts	/dev/pts	Pseudo terminals
mqueue
binder	/dev/binderfs	Android binder IPC
pstore	/sys/fs/pstore
bindfs
fuse
fusectl	/sys/fs/fuse/connections
autofs		按需挂载和卸载
specfs	/dev/streams	不需要挂载
tmpfs	/tmp,/run
ramfs
pipefs	pipe:	当 shell 使用 pipe 时
loopfs	/dev/loop*
rootfs	/
fscache
erofs		Enhanced Read-Only FS

• https://docs.kernel.org/filesystems/erofs.html
• erofs
  • https://docs.kernel.org/filesystems/erofs.html
  • https://en.wikipedia.org/wiki/EROFS
  • Linux 5.4+
  • by Huawei, Alibaba Cloud, Bytedance, Coolpad, Google, OPPO
  • 多用于 Android
  • 添加压缩，内容寻址
  • EROFS over Fscache - Linux 5.19+
    • by Alibaba Cloud for RAFS v6/Nydus
• fscache
  • https://www.kernel.org/doc/Documentation/filesystems/caching/fscache.txt
  • https://docs.kernel.org/filesystems/caching/fscache.html
  • cachefilesd
  • /proc/fs/fscache/caches
  • /proc/fs/fscache/volumes
  • /proc/fs/fscache/cookies
  • /sys/module/fscache/parameters/debug
• rafs
  • RAFS v6 兼容 EROFS
  • https://d7y.io/blog/2022/06/06/evolution-of-nydus/
• /dev/ptsmx - terminal mulitplexer
• max filename length
  • 255 bytes
    • ext4, zfs

逻辑

fs	notes
overlayfs
unionfs
aufs	v1 AnotherUnionFS, v2 Advanced multi-layered Unification fs

物理/硬盘

fs	notes
ext3
ext4
zfs
ntfs
exfat
xfs
erofs	Enhanced Read-Only File System¶
squashfs	live-distro - 替代 cramfs
omfs	Optimized MPEG Filesystem
initramfs	INITial RAM FileSystem
initrd	Initial Ramdisk
cramfs	Compressed RAM/ROM FileSystem - 嵌入式替代 initrd

网络

fs	notes
nfs
smb
cifs
pvfs2	OrangeFS
juicefs
davfs2	WebDAV
ftpfs
sshfs
gfs2	Global File System by RedHat

cat /proc/filesystems # 支持的 fs
ls /proc/fs/          #  fs 模块
cat /proc/mounts      # 挂载情况

# https://www.kernel.org/doc/html/latest/filesystems/debugfs.html
mount -t debugfs none /sys/kernel/debug

# https://docs.kernel.org/admin-guide/binderfs.html
mkdir /dev/binderfs
mount -t binder binder /dev/binderfs

mount -t specfs none /dev/streams

• List of file systems
• https://www.deepanseeralan.com/tech/some-notes-on-filesystems
• vgough/encfs
• Docker fileshare
  • FUSE
  • gRPC over Hypervisor sockets

bind

• 系统 将一个 目录 挂载 到一个挂载点
  • 一般是 挂载 设备
• 类似 symlink - 但不依赖应用 lookup
• 类似 hardlink - 但不依赖 fs
• 参考
  • FUSE 实现 https://bindfs.org/
  • FreeBSD nullfs mount -t nullfs /a /b

mount --bind /a /b          # 也可以使用 -o bind
mount --rbind /c /b         # 重新 bind
mount -o remount,ro,bind /b # 重新设置为 只读
mount --move /b /d          # 移动挂载点